Temperature changing system



Aug 16 1933 D. G. TAYLOR TEMPERATURE CHANGING SYSTEM Filed Sept. 5, 41935 mziel Gf Iglo?" systems of Patented Aug. 16, 1938 lUNITI-:o STATES PATENT OFFICE.

TEWERATURE il Daniel G. 'laylon Minneapolis, i i

@ING VSYSTEM :i w assignor to Minneapolis-Honeywell Regulator lompany, Minneapolis, Minn., a corporation ol llielaware `dpplication September 5, i935, Serial No. 39,293

lill @laimu sponsive to outdoor'atmospheric conditions, in-

dit

lill

cluding temperature, wind, and solar radiation lor controlling the temperature within the building. Heating means are provided in the bullding for supplying heat to the building and heating means are also providedin the outdoor controller ior supplying heat to the outdoor controller. The two heating means are proportioned according to the heat losses from the building and from the outdoor controller. A thermostatic device is provided lor responding to the temperature within the outdoor controller and when this thermostatic device calls for heat both of the heating 4nuaans are energized to deliver heat to the building and to the outside controller. Due to the proportional relationship of' the heating means with the heat losses of the building and the outside controller, a definite temperature relation is maintained within the building and the outside controller so that by responding to the temperature oi the outside controller, the thermostatic device maintains a constant or normal temperature within the building.

From the above it follows that the temperature changing system disclosed in my copendlng application measures the heat demand and controls the amount or heat supplied to the building purely as a time function and in order for the amount ofv heat supplied to the building to be proportional to the demand for heat, or to the arnountof heat supplied to the outdoor controller, it is necessary for the outdoor controller to control some source oi heat in which the amount of heat supplied is in direct proportion to the operating time. In other. words, upon a call lor heat by the outdoor controller tor a given interval ol time, a given amount-oi heat must be supplied to 'the building. This is Ksubsiantially true oi steam valves controlling the supply otA steam to a building trom a source maintained at 'approximately constant pressure and it` is also substantially true where the outdoor controller controls an oil or gas burner. I-loweven, in the case ol such heat sources as stokers, etc. demand by the outdoor controller for operation lor a denite length'or time does not give any accurate measure ol the amount oi heat delivered-ln that time since under favorable conditions oi dralt iuel bed, etc., severaltimes as much heat may be f ing mechanism used in Fig. l.

(Cl. 23d-ll.)

supplied in a given time as will be supplied when these conditions are less favorable.

It is therefore an object of this invention to' remedy the above defects in the described system wherein the heat source is controlled by a Stoker, etc.v

u More specifically, it is an object or this invent1on o provide a means for determining or measurlng the amount of heat required to be delivered to the building, means for determining or measuring the actual amount of heat delivered to the building and means for correlating these two means into a control device for controlling thev operation of a stolrer or the like whereby truly proportional amounts of heat may be accurately determined and delivered to the outdoor controller andthe building.

The novel manners in carrying out this type of control for a temperature changing system also provide objects oi this invention.

@ther objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying speciiication, claims and drawing in which:

liig. l is a diagrammatic illustration of the preferred iorm of my invention.

Fig. 2 is a partial sectional view oi the switch- Fig. 3 is an enlarged sectional view taken substantially on the line l-t of Fig. 2 but with the retaining plate omitted for purposes oi clearness.

Referring to Fig.' l, the temperature changing system ol this invention is shown as applied to a building having an outside wall it 'and a plurality oi spaces tobe conditioned one of which is shown at ll. Although this invention in its broad aspect contemplates 'a cooling system, as well as a heating system, for purposes of illustration l' have shown a particular type of heating system winch may taire the form of a steam heating system. Located in the spaces to be heated il are radiators or heatl exchangers il to which steam is supplied by means of risers it. The usual radiator valves il are connected between the risers lt and theradiators il. The risers il are connectedI into a steam header it which in turn is connected to a boiler il! by a steam supply pipe, it, Therefore, when steam is generated in the boiler ll, it passes through the supply pipe it, the header lb and the risers lt/into the radiators il to be condensed therein. Water or. condensation is returned to tbeboiler il from the radiators il through the conventional steam traps it, the return risers it, return header 20 and retumpipes 2l and tt. Connected between the vto return pipes 2IA and 23 is a condensate meter 22 of usual dign for performing a control function in the manner to be pointed out hereafter. By employing the steam traps I3, condensate only is allowed to return to the boiler as is usual in heating systems of this type. A steam trap 24 is located between the supply header I and the return header 20 to drain oif any condensate that may form in the high side of the steam heating system. The above described steam heating system is well-known in the art and any other appliances that are used in such heating systems may be applied in the system brieflydescribed.

'Ihe boiler I1 is shown as being fired by a stoker 25 although any other type of firing means may be used. 'I'he stoker 25 is of usual design and is operated in the usual mannerby an electric motor 23. A high limit pressure switch 21 of usual design is yprovided in the boiler to prevent the forming of undue pressure therein. 'Ihis high limit pressure switch 21 contains' a mercury switch 23. The stoker motor 23 is connected by a wire 29 to a line wire 3l).v The other line wire 3I is connected by a wire 32 to a contact 33. Cooperating with the contact 33 is a switch arm 34 which ls connected by a wire. 35 to one electrode of the mercury switch 23 operated by the high.1imit pressurev device 21. The other electrode of the mercury switch 23 is connected by a wire 33 to .the stoker motor 23.

When the switch arm 34 is moved into engagement with the contact 33 in the manner to be pointed out hereafter, a circuit is completed from the line wire 3| through wire 32, contact 33switch arm 34, wire 35, mercury switch 23, wire 33, stoker motor 23 and the wire 29 back to the other line wire 30. Completion of this circuit causes operation of the stoker 25 and consequent flring of the boiler I1 whereby steam is generated and delivered to the heat exchangers or radiators I2. As pointed out above, the time required to deliver steam to the heat exchangers or radiators I 2 upon closure of switch arm 34 with the contact 33 varies from time to time depending upon the condition of the draft, fuel bed. etc. Upon movement of switch arm 34 out of engagement with the contact 33 or upon the existence of an abnormally high pressure in the boiler I 1 so as to tilt the mercury switch l23 into a circuit breaking position, the stoker 25 is placed out of operation to prevent the further generation of steam.

A contacting or switching mechanism is generally shown at 43 and byreferring to Figs. 2 and 3, the details of construction are shown therein. This switching mechanism 43 comprises a collar 4I, loosely mounted on a normally stationary shaft `42, the collar 4I being provided with an integral electrical conducting sleeve 43. The shaft 42 is provided in any suitable manner with an enlargement 44 which is positioned within an enlarged bore 45 in the collar 4I. The enlarged portion 44 of shaft 42 is provided with anabutment key 43 and diametrically -positioned from the abutment key 43 is' another abutment key 41 carried by the collar 4I. Located .between the abutment keys 43. and 41 are diametrically opposed springs 43 and 49. These springs 43 and 43 are equally tensioned so as to tend to maintain the abutment keys 43 and 41 diamtrically spaced.

.The keys 43 and 41 and the springs 43 and 49 form/a two-way strain release connection between the'shaft 42 and the collar 4I so that the shaft 42 andthe collar 4I may be rotated with respect to each other but the strain release rection.

Awheel 32 and shaft 42 remain stationary. The

connections between the shaft 42 and the collar 4I tends to maintain these elements in the position shown in Fig. 3.v The springs and keys are held in place in the enlarged bore 45 of the collar 4I by means of a. plate 50 suitably secured to the collar 4I. Secured to the collar 4I and in electrical contact therewith is a contact arm 5I.

A shaft 53 is provided with an insulating sleeve 54 on which 'is mounted a collar 55, having an integrally formed conducting sleeve 56. The collar 55 is insulated from the shaft 53 by an insulating sleeve 54 and is non-rotatablyv mountedv on the shaft 53 in any suitable manner such as by means of a pressed fit. The collar 55 is provided with a contact arm 51 which extends outwardly adjacent to the contact arm 5I. Spaced from the collar 55 and mounted on the sleeve 56 is a collar 59, having an integral conducting sleeve 60. The collar 59 is non-rotatably secured on the sleeve 56 in any suitable manner such as by a pressed t. The collar 59 is provided with a contact arm 6I"which extends outwardly adjacent the other side of the contact arm '5I of the collar 4I.

Assume the parts in the position shown in Fig. 1 with the contact 5I spaced midway between the contacts 51 and 6I. Movement of the shaft 53 in a counter-clockwise direction as viewed in Fig. 1 causes movement of the contact arm 5I into engagement with contact 5I. Continued counter-clockwise movement of shaft 53 causes counter-clockwise movement of both Contact arms 3| and 5I, this continued movement being permitted by the strain release connection between the contact 5I and the normally stationary shaft 42. Upon stopping of the rotation of kthe shaft 53 and upon counter-clockwise rotation of shaft 42 .the strain release connection is relieved and when the springs 48 and 49 become equally tensioned by this counter-clockwise movement of shaft 42 the contact arm 5I moves out of engagement with the contact arm 6 I. Continued counter-clockwise movement of the shaft 42 causes movement of the contact arm 5I into engagement with the now stationary contact arm 51. Continued movement of the shaft 42 is permitted by reason of the strain release connection between the contact arm 5I and the shaft 42. Although it has been assumed in this description of the operation of the switching mechanism that one or the other of. the shafts 42 and 53 is stationary, it will be seen that relative movement of these shafts will cause substantially the same operation.

v 'I'he condensate meter 22 is diagrammatically shown to comprise a bucket wheel 32 so that when condensate flows from the return header 23 tow the boiler I1, the bucket wheel 32 is rotated in a counter-clockwise direction as viewed in Fig. 1 to'rotate the shaft 42 in a counter-clockwise di- When no condensate is flowing, the

shaft 53 is driven in a counter-clockwise direction through a reduction gear train 63 by a rotor 34 upon energization of a field 35. The conducting sleeves 53, 60 and 43 are contacted by brushes or fingers 61, 33 and 39, respectively, so that when the contact arm 3I is moved into engagement with the contact arm`5l, an electric circuit is completed from the brush 33 to the brush 39 and when the contact arm 5I is moved into engagement with the contact arm 51, 'an .electric circuit is completed from the brush 61 to the brush 33.

A primary 12 of a step-down transformer 13,

:lili

having a secondary 1l is connected across the line wires 30 and 3| by wires 10 and 1i, respectively. A relay comprising an energizing coil 15 and a bucking coil 1li operate a switch arm 18 and the switch arm 34.' Upon energization of the energizing coil 15, the switch arms 18 and 34 are moved into engagement with a contact 1l and the contact 33, respectively. Upon energization of the bucking coil 16, which neutralizes the action of the energizing coil 15, the switch arms 18 and at are moved out of engagement with their contacts 'il and 33 by means of springs or gravity or other means, not shown. Likewise, when neither energizing coil 15 or bucking coil llt is energized,

the switch arms 1d and it are maintained out of engagement with their contacts ll and it, respectively, by means oi springs, gravity or other means, not shown.

One end of the secondary 'it is connected by 'a vwire til -to one end of the energizing coil it.

The other end of the energizing coil it is connected by wires il and tit to the brush ti. One end ot bucking coil it is connected by a wire tit to the junction of wire t@ with the energizing coil it. The other end oi bucking coil it is connected by a wire til toV the'brush. tl. The brush tt is connected by a wire til to the switch arm it and the switch arm it is in turn connected by a wire tt to the other end of secondary it. it wire tl connects the contact 'il with the junction of wires ti and it.

When the contact arm t i Ais moved into engage. l

ment with the contact arm ti, a circuit is completed from the secondary it through wire it, f energidng coil it, wires ti and it, brush it,

conducting sleeve dit, collar iii, contact arm ti, contact arm ti, collar tt, conducting sleeve til, brush tt, and wires 'it and it bach to the secondary it. Completion oi this circuit energizes the energizing coil to move the switch arms it and it into engagement with the contacts 'lli and ti. Movement of the switch arm it into engagement with the contact it places the stolrer it in operation with the consequent generation ci vsteam in the boiler it and delivery oi steam -to the heat exchangers or radiators ii. Movement ci the switch arm it into engagement with the contact 'lill completes a maintaining circuit trom the secondary it through wire itil, energinngcoii "iii, wires iii and til, contact il', switchg-ams it fand wire tt bach to the secondary ld. A@chipietion ci this maintaining circuit maintains the relay coil lli energized even though the contact arm ti moves out -oi engagement with the contact arm ti thus maintaining the boiler hired.

Water or condensation iorined in the radiators ii returns through the return risers iii, the return header it and the return pipe il into the condensate meter iii.' This causes rotation ot normally stationary buclret wheel ti and consequent counter-clochwise rotation oi the normally stationary shait di. When sumcient rotation of shaft iii has talcen place to move the contact-arm il into 'engagement with the contact arm tl, a circuit is completed irom the secondary it through wires it and titl, bucmng coil it, wire til, brush til, conducting sleeve tt, collarv it, contact arm il, contact arm ti, collar iii, conducting sleeve di, brush tt, wires ti and tl, contact il, contact 'arm 'it and wire tt bach tothe secondary it. Completion of this circuit causes energization oi bucking coil 'it which neutralizes the holding vaction of the energizing coil it whereby the switch arms 'it and it are moved outof'engagevmoment lwith their contacts 11 and 3i.' Movement of switch arm 3l out of engagement with the contact 33 prevents the further operation oi stoker 25 and the further generation of steam in the boiler I1. Movement of switch arm 18 out of engagement with the contact 11 maintains both the energizing coil 15 and the relay coil 16 deenergized until the contact arm 6i is again moved into engagement with the contact arm I to energize the energizing coil 15 in the manner pointed out immediately above. l

Located outside of the building in any suitable manner is an outdoor controller, generally designated at t9. The outdoor controller tt comprises a block it which is hollowed out to receive a bimetallic element si suitably mounted on a post il. The bimetallic element 9i responds to the temperature of bloclr si and in `order to insure that it will not be directly aiected by outside temperatures, the block Si is closed by means oi'a cover it. The bimetallic element si ,carries contacts it and it which are adapted to sequentially engage contacts it and @l which are adjustably mounted in an insulating block si fcarried by the metallic block it. Thedstance between the contacts @il and @t is less than the distance between the contacts it and il so that upon a decrease in temperature o block it, the contact iii iirst engages the contact it and upon a further decrease in temperature, the contact it engages the'contact il. The block it is heated by a heater @i and is cooled by the outdoor atmospheric conditions. The above mechanism comprising the outdoor controller it is enclosed within a weathertight casing tilt to protect the same from deterioration by the. elements.

it primary iti oi a step-down transformer itt, having a secondary itt is connected across the line wires it and il. A relay coil designated at itt operates switch arms itt and itl so that upon energization oi the relay coil itt, the switch arms itt and itl `are moved into engagement with contacts itt and itt. Upon deenergization oi relay coil itt, the switch arms tilt and itl are moved'out oi engagement with the contacts lili and tilt by means ot springs, gravity, or other means, not shown.l One end oi' secondary litt is connected bya wire lili to the adjustable contact The other adjustable contact il is' nected by a wire itil to the junction ci wires iii and iii. The contact itt cooperating with the switch arm itt .is connected by a wire iii to the bimetallic element il located in the outdoor controller til. *A

.The contact liti is connected by a wire llt to the line wire il. The switch arm itil cooperating with the contact itt is connected by wires ill and lit to a variable resistance or rheostat iii. The variable resistance or rheostat liti' is in turn connected by a vnre lit to an ammeter lil. The ammeter iii is connected by a wire iii to one end oi heater it of outdoor controller tt. The other end ci the heater it is connected by wires iii and iid to the other line wire it. One end of the Held ttassociated with the rotor tt' is connected by a wire lit to the junction oi wires lili and lit. The other end oi ileld Gt is connectedby a wire y llt to the junction oi wires lit and iti. By Vreason oi' these electrical connections, the eld t5 and the heater @it are connected in parallel so thatwhen heater tt is enersized, the field $5 is likewise energized. The

afforded means for adjusting and visually indicating the amount of heat delivered to the block 90 and the heater 99.

When the temperature of block 90 falls to a predetermined value, the contact 94 is moved into engagement with the contact 96 and when the temperature of the block falls below this predetermined value, the contact 95 is moved into engagement' with the contact 91 to complete a circuit from the secondary |04 lthrough wire H0, contacts 96, 94, 95 and 91, wires IH and H2, relay coil |05 and wire H3 back to the secondary |04. Completion of this circuit causes energization of relay coil |05 to move the switch arms |06 and I 01 into engagement with their respective contacts |06 and |09.

Movement of switch arm |01 into engagement with the contact |09 completes a circuit from the line wire 3| through wire H6, contact |09, switch arm |01, wires H1 and H8, variable resistance H9, wire |20, ammeter |2|, wire |22, heater 99 and wires |23 and |24 back to the other line wire 30. Movement of switch arm |01 into engagement with the contact |09 also completes a circuit from the line wire 3| through Wire H6, contact |09, switch arm |01, Wires H1 and |25, field 65 and wires |26 and |24 back to the other line wire 30. Completion vof these two circuits causes simultaneous energization of the heater 99 and the field 65, 'I'his causes heating of block 90 and rotation of shaft 53 in a counterclockwise direction to move the contact arm 6 |into engagement with the contact arm 5|.

Movement of switch arm |06 into engagement with the contact |06 completesl a maintaining circuit from the secondary |04, through Wire H0, contacts 96 and 94, bimetallic element 9|, wire H5, contact |08, switch arm |06, Wires H4 and H2, relay co'il |05 and wire H3 back to the secondary |04. Completion of this circuit maintains the relay coil |05 energized to maintain the switch arms |06 and |01 in engagement with their contacts |08 and |09 until the temperature of block 90 has risen sufficiently to break contact between the contacts 94 and 96. When the temperature of block 90 has risen to the value which is suiil# cient to break contacts 94 and 96, the relay coil |05 is deenergized to move the switch arms |06 and |01 out of engagement with the contacts |08 and |09. This causes deenergization of the heater 99 and the field 65. The block 90 is then allowed to cool and further rotation of shaft 53 is prevented.

When the temperature of the block 90 is cooled by the outdoor atmospheric conditions so as to cause energization of the relay coil |05, heat is supplied to the block 90 and the shaft 53 is rotated in a counter-clockwise direction. Such a counter-clockwise rotation of the shaft 53 causes engagement of the contact arm 6| with the contact arm 5| to cause energi'zationV of the stoker 25 with the consequent generation of-steam in the boiler I1. Heat will be supplied to the block 90 and the shaft 53 and contact arms 6| and 5| will continue to be rotated in a countelrclockwise ldirection until the bimetallic element 9| is satisfied. On relatively cold days the length of time required to bringl the block 90 up to temperature so as to deenergize the relay coil |05 will be longer than on relatively warm days. Since the field 65 associated with the rotor 64 is energized simultaneously with the heater 99, the contact arms 51 and 59 will be positioned farther along in a counter-clockwise direction on a cold day y 2,127,472 variable resistance- H9 and the ammeter |2| than on a Warm day. I'his extended movement of the contact arm 6| beyond its point of engagement with the contact arm 5| is permitted by the strain release connection between the collar 4| and the normally vstationary shaft 42.

When the boiler |1 is thus energized to generate steam and deliver the same' to the heat exchangers or radiators I2, heat is supplied to the building by reason of the steam condensing in the radiators l2. Condensate flows from the radiators l2 through the condensate meter 22 in the manner pointed out above, and rotates the shaft 42 in a counter-clockwise direction. When the shaft 42 has rotated sufiiciently far by the condensation of steam so as to take up the lost motion in the strain release connection, and to move the contact arm 5| into engagement with the contact arm 51, the stoker 25 is stopped to prevent the further vgeneration of steam in the boiler l1 and the delivery of such steam to the radiators |2. In other words, when sufficient steam has'been condensed in the radiators to supply a suilcient -amount of heat to the building so as to move the contact arm 5| into engagement with the contact arm 51, the further supply of heat tothe building is stopped. Since more counter-clockwise movement of the contact arms 51 and 6| is afforded during'cold weather than during warm weather, it follows that the shaft 42must also move farther ina counterclockwise direction on colder days than on warmer days. Therefore more condensate must be delivered to the condensate meter 22 during cold Weather than during warm weather, which.

means that more heat is delivered to the building during cold weather than during warm Weather. By use of the condensate meter 22 and the switching mechanism 40 operated thereby, the actual amount of heat delivered to the building is accurately determined and correlated with the amount of heat delivered to the outdoor controller 89. The capacity of the condensate meter. the speed of rotation of the shaft 53 by the motor rotor 64, and the amount of heat delivered to the outdoor controller 89 under the control of the rheostat or variable resistance H9, are so selected and designed that the amount of heat actually delivered to the outdoor controller is proportioned to the amount of heat actually delivered to the building as the heat losses of the outdoor controller are to the heat losses of the building.

From the above it is seen that I have provided a means for determining or measuring the amount of heat required tol be delivered to a building, a means for determining or measuring the amount of heat actually delivered to the building, and means in the form of a switching mechanism for correlating the action of these two means for controlling a firing means such as a.

stoker for a boiler. In this manner the amount of heat actually delivered to the outdoor controller 89 and to the building is definitely ascertained and proportioned, whereby a substantially constant temperature is maintained within the building in accordance with outdoor atmospheric conditions, including temperature, wind and solar radiation regardless of the condition of the fire bed and draft in the boiler at the time the call for heat is established.

Although I have disclosed one specific embodiment of ,my invention, various vmodifications thereof may become apparent to those skilled in the art and therefore this invention is to be limexchanger means in a space the temperature of f which is to be controlled, means for delivering uid to the heat exchanger means, means re-Y sponsive to a condition indicative oi' the temperature changing load for starting operation of the delivering means, and means responsive to the amount oi uid. delivered to the heat exchanger means for stopping operation oi the delivering means.

3. In a steam heating system for a building, heat exchanger means, a boiler for supplying steam to the heat exchanger means, firing means for the boiler, and means for controlling said firing means including means responsive to outdoor atmospheric conditions including temperature, wind and solar radiation and means responsive to the amount of steam delivered to the heat exchanger means.

d. In a steam heating system for a space having heat exchanger means, a boiler and a stoker therefor, means for measuring the heating load of the space, a condensate meter, and switching mechanism operated by said condensate meter and said measuring means for controlling said stoker.

5. In a steam heating system for a building having heat exchanger means, a boiler and a stoker therefor, an outdoor controller for measuring the heating load of the building, a condensate meter, and switching mechanism operated by said condensate meter and said outdoor controller for controlling said stoker. v

6. In a steam heatingl system ior a building, 'heat exchanger means, a boiler and a firing means, an outdoor controller subject to the same atmospheric conditions as the building, heating means for the outdoor controller whereby the outdoor controller is affected by temperature, wind and solar radiation, means responsive to the temperature of the outdoor controller, a condensate meter responsive to the amount of steam condensed in said heat exchanger means, and` switching mechanism operated by said condensate meter and said thermostatic means for controlling said ring means. i

7. In a steam heating system for a building, heat exchanger means, a boiler and a nring means, an outdoor controller subject to the same atmospheric, conditionsas the building, heating means for the outdoor 'controller whereby the outdoor controller is aiected by temperature,`

'wind and solar radiation, means responsive to the temperature of the outdoor controller, a condensate meter responsive to the amount of steam condensed in saidv heat. exchanger means, an electric motor, the-controller heating means and the electric motor being energized when said thermostatic means calls for heat, a switching :mechanism operated by said electric motor and said condensate meter for controlling said ring means.

8. In a heatingsystem for a building, means for supplying heat tothe building, means for measuring the amount of heat supplied to the building, a device located outside of said building and having heating means to cause said device to be aected by outdoor atmospheric conditions including temperature, wind and solar radiation whereby said device measures the heat loss from said building, and control means operated by said device for supplying heat to the building, said control means also operated by said measuring means rior stopping the supply of heat to the building,

9. In a heating system for a building, means ior supplying heat t' the building, a device located outside of the building and subject to the same atmospheric conditions as the building, 'said device including heating means and thermostatic means, means controlled by the thermostatic means for energizing and deenergizing'the heat-` ing means of the device to maintain the temperature of the device within desired limits, control means operated by the thermostatic means simultaneously with the energizatlon of the heating means of the devicefor measuring the heatv loss from the building, control means for measuring the amount ofheat supplied to the building, and means controlled by the conjoint action of both control means for controlling the building heat supplying means.

l0. In a heating system for a building, means for supplying heat to the building, a device located outside of the building and subject to the same atmospheric conditions as the building, said device including heating means and thermostatic means, means 'controlled by the thermostatic means for energizing and deenergizing the heating means of the device to maintain the temperature of the device within desired limits, control means operated by the thermostatic means simultaneously with the energization of the heating means of the device for measuring the heat loss from the building, control means for measuring the amount of heat supplied to the building, means controlled by the rst control means for. supplying heat to the building upon a call ior heat and controlled by the second control means for interrupting the supply of heat to the building when the correct amount of heat has been supplied to the building to makeup for the heat loss therefrom.

DANIEL G. TAYLOR. 

